The invention relates generally to the field of work piece alignment, and in particular to work piece alignment on turning machines. More specifically, the invention relates to work piece alignment on turning machines to remove radial misalignment (runout) between the work piece and the rotary axis.
In turning machines, such as lathes, ultra-precision grinders, and single point diamond turning machines, the work piece must be lined up exactly with the rotary axis to which it is attached. If the work piece is not aligned correctly at the beginning of the operation, precision and accuracy of the finished piece is compromised. The movements of the cutting tool are set precisely to coincide with the alignment of the rotary axis of the toolholder, and therefore, the work piece must be lined up exactly with the rotary axis of the toolholder for the machining operation to be successful.
Runout, characterized by uneven off-center motion, occurs when the alignment of the work piece is not present or not perfect. This results in machining errors on the work piece, and also adds more wear to the cutting tool. Since the motion is uneven, the edge of the tool is not worn evenly. Alignment must remain precise during the work operation.
Traditional removal of radial runout consists of mounting a work piece on either a vacuum or magnetic chuck, and tapping the work piece in the opposite direction of offset until radial runout is reduced to a satisfactory level as measured with an indicating device. Alignment in this traditional manner requires a high level of skill to achieve a reduction in radial runout efficiently. Relocation of the work piece by tapping it back and forth may result in adjustment overshoot and further misalignment in other directions, thus requiring additional alignment. These steps cost time and energy and often results in frustration
There have been numerous prior art attempts to resolve the aforementioned problems. To solve the problem of runout, some devices depend on elaborate designs for both the toolholder and the work piece that are costly to manufacture. In other developments, the alignment may be adjusted by very complicated arrangements: pre-alignment bores and meshed tooth sets (PCT No. WO 99/42238 issued to Kevin J. Bisset on Aug. 26, 1999); jaws connected to drives with gear trains (U.S. Pat. No. 4,718,682 issued to Antun Zilic et al. on Jan. 12, 1988); jaws, motors, and a clutch (U.S. Pat. No. 4,209,180 issued to Mario Bertorello on Jun. 24, 1980); and piston and ball lock assemblies (U.S. Pat. No. 6,375,398 issued to Jack R. Gaudreau et al. on Apr. 23, 2002).
Other attempts to address this problem include devices that require a particular tool end working with a particular toolholder to secure the alignment. Most of them require a shank and collet with a cylindrical shaped housing to accept the tool end. Such devices are disclosed in: U.S. Pat. No. 3,790,182 issued to Robert H. Schuman on Feb. 5, 1974; U.S. Pat. No. 3,599,996 issued to Donald G. Holt on Aug. 17, 1971; U.S. Pat. No. 5,882,015 issued to Ronald L. McPherson on Mar. 16, 1999; and U.S. Pat. No. 6,375,398 issued to Jack R. Gaudreau et al. on Apr. 23, 2002. Misalignment and runout can be controlled only if the toolholder and tool ends are manufactured exactly as described in these patents. Different types of work pieces with different tool ends would not be acceptable.
The size of most of the devices cited in the aforementioned patents cannot be adjusted significantly. Because of the mechanisms built into the toolholder or the tool end, reducing the size of the device would be difficult if not impossible. (See, for example, the devices as depicted in U.S. Pat. No. 4,718,682 issued to Antun Zilic et al. and U.S. Pat. No. 4,209,180 issued to Mario Bertorello.) These devices cannot be made significantly smaller.
Skilled artisans will appreciate that there are other devices made for specialized purposes and, although effective for their specialties, offer no versatility. The device disclosed in U.S. Pat. No. 4,209,180 (Bertorello), for instance, is made for large, heavy machining operations. Moreover, devices disclosed in U.S. Pat. No. 3,595,591 issued to Roland G. Koch et al. on Jul. 27, 1971 and U.S. Pat. No. 5,882,015 (McPherson) are floating toolholders, focused on machines that complete precise holes or threads.
One skilled in the art will appreciate that a device, like the one described in U.S. Pat. No. 4,583,432 issued to Michael W. Bricker on Apr. 22, 1986, for instance, involves the completion of a two-step process to set the alignment. In the first step, it is required to set the coarse adjustment and then set the precise adjustment by turning four fine adjustment screws in appropriate sequential rotation. Such process steps add complexity and time consuming adjustment to such an alignment operation.
Another device as described in PCT No. WO 99/10785 issued to Patrick Boland, et al. on Mar. 4, 1999, requires a CNC computer to align the work piece accurately.
Therefore, a need persists in the art for an eccentric toolholder that allows for radial offsets to be separated along two perpendicular axes, which may then be independently adjusted for precise alignment. The toolholder of the invention eliminates run-out and can be used for many different types of work pieces. Moreover, the toolholder is relatively compact and easily manufactured.
It is an object of the invention to provide a work piece holder device that maintains the work piece in alignment during rotary movements.
Another object of the invention is to provide a work piece holder that compensates for work piece run-out during operation.
Yet another object of the invention is to provide a method of aligning a work piece during rotary operations.
It is a feature of the invention that aligning members, structurally associated along the rotary axis of a rotary unit, holds a work piece aligned relative to the rotary axis in response to pivotal movements of the aligning members during operation.
To accomplish the aforementioned objects, advantages and features of the invention, there is provided, in one aspect of the invention, a method of alignably supporting a work piece for rotary movements. The method comprises the steps of: providing a work piece holder comprising a plurality of cooperating aligning members, wherein one of the plurality of cooperating aligning members has a bore opening for retaining the work piece for rotary movements about a rotary axis and wherein at least one of the plurality of cooperating aligning members is adapted to pivotable movements in one direction in response to work piece runout, and another of the plurality of cooperating aligning members being adapted to pivotable movements in another direction substantially orthorgonal to the one direction in response to another work piece runout; disposing the work piece securely in the bore opening for rotary movement; and adjustably aligning the work piece relative to the rotary axis in response to pivotable movements of the plurality of cooperating aligning members on the rotary axis.
The present invention has the following advantages:
In applications where concentric alignment is needed between a rotary axis and a cylindrical part, the disclosed device provides a means for quick and precise removal of radial runout by allowing eccentric adjustment along two perpendicular axes. The device is compact and lightweight consisting of only three small disks or plates, thus providing advantage for applications that have weight limitations and/or space constraints.